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AGRO-ECOLOGICAL BLOGFARMLAND ASSETS: THE MARVELLOUS MATTERSoil Organic Matter (SOM), not exactly the sexiest topic you might think. Probably not a hot topic of discussion amongst the super level of PE and Hedge Fund GPs....but if you enjoy eating from time to time and/or if you are investing in farmland then it is a topic you may wish to consider. As with so many topics in farming, particularly ecologically literate farming it is possible to go deep into detail and levels of discussion/explanation but as this is a blog and not a research paper we will be attempting to keep things relatively short and simple. In farming we are seeking to use our understanding of ecological science in order to create an optimal agro-ecosystem (including SOM) to generate the most robust and therefore successful system we possibly can. SOM is connected to production performance and resilience, the latter of which is critical in farming systems now and increasingly so as climatic stress increases. Where soils are exploited without restoring organic matter, enhancing soil biological activity and maintaining good structure, nutrient cycles are broken, soil fertility declines and the robustness and health of the agro-ecosystem is compromised. The consequences of that are all too well known and obvious. What is Organic Matter? Soil Organic Matter is the product of biological decomposition (plant and animal) on site, i.e. in the paddock/ field. It provides nutrients and habitat to soil microorganisms, enhancing their diversity and activity with benefits including reduced pathogens and diseases (amongst others), it improves soil structure, water holding capacity, resistance to erosion and compaction and is a nutrient reservoir for plants. It is often described as being at the very foundation of soil ecology and management. Many standard agricultural practices, such as intensive-tillage, soluble nitrogen fertilisers and stubble burning, accelerate the decomposition of soil organic matter and leave the soil susceptible to erosion by wind and water. This releases carbon into the atmosphere while also reducing the long-term productive ability of the land. It is important to remember that without soil there is no life and that there is a close correlation between failed civilisations and soil degradation/loss (on this topic I recommend David Montgomery’s Dirt: The Erosion of Civilisations). How best to manage? There are management practices that enhance soil health and generate sustainable agricultural productivity. Good practices such as minimum tillage, cover crops and sound rotations. The relatively recent industrial farming systems have tended to mine the soil for nutrients and to reduce soil organic matter levels through repetitive harvesting of crops and failure to attend to/restore soil quality other than via a bag of synthetic fertiliser, which in itself also works against the best interests of the soil and management independence from external inputs. This decline in soil quality/organic matter content will continue until farm and specifically soil management practices are improved. Only well designed diversified cropping systems and/or competently managed mixed cropping/livestock systems are able to maintain a suitable balance in nutrient and organic matter provision and utilisation. Ecological agriculture uses holistic management systems that promote and enhance the health of the agro-ecosystem, including above and below ground biodiversity, biological cycles, and biological activity. These systems apply specific and precise standards of production practice based on minimum-tillage techniques, cover crops and effective rotations. Through intelligent harnessing of agro-ecological processes, ecological agriculture provides an opportunity for reducing external inputs and for converting low-input agricultural systems into significantly more productive ones. A better understanding of the linkages between soil biology and ecosystem function and the impact of human actions encourages the reduction of negative impacts and the improved utilisation of beneficial soil biological activity for sustainable and productive agriculture. There are many possible sources of fresh organic matter that can be added to soil for the creation of soil organic matter. The individual crops that are grown will contribute material that remain in the soil and will ultimately become SOM. Cover crops and/or green manures can also provide food for the soil food web and therefore the development of soil organic matter. Animal manure is a primary component added to the soil to enhance and develop soil organic matter (a key advantage of all year pastoral grazing systems) as is compost particularly in those systems/climates where animals are housed inside for large periods of time. Conclusion Soil organic matter contributes significantly to soil quality, plant health and agro-ecosystem resilience. Managing soil organic matter demands the consideration and understanding of a complex range of factors. Genuinely sustainable management seeks to continually expand its understanding of soil and through the application of effective ecological management practice to enhance the asset that is soil organic matter. Comments on this blog
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